Measuring voltage from micro

One alternative might be to use a smarter temeprature sensor, such as a DS18S20 that delivers the temperature as a digitally rather than as a voltage. You'd need to implement a 1-wire bus, but there seem to be implementations available for most micros which would make it pretty easy to integrate into your existing code.

"Poxy" wrote

You'd need to implement a 1-wire bus,

Brian Goldsmith

Prehaps I should have said "1-Wire Bus TM" - a well known and well-defined product with a wealth of information available for those who'd prefer to learn and understand. I'd kindly suggest you follow the link I provided if you're interested in that "learning and understanding" thing I mentioned.

Doesn't sound like the ideal solution to me.

Michael

I've ordered this one from futurlec. As I'm already using I2C with 2 chips I've already got working code. Hopefully it will just be a matter of plugging it in :-)

Michael

The 1-wire bus is a *dog* of a thing to implement and places timing restrictions on your system. If you need up to 8 sensors or so I suggest a more popular I2C sensor rather than 1-wire.

I2C master code is very simple and not timing sensitive.

-Andrew M

I ordered an I2C ADC a couple of weeks ago, received it yesterday and soldered it into my prototype tonight. The code I'd written for the eeprom worked with it straight off. Now I've just go to work out how to convert a resistance that varies from 40ohm to 1k into a voltage from 0 to 2.5 and keep enough accuracy at the 40 ohm end of the scale.

I'll see how I go with noise, if it's a problem I'll see what I can do. I'm already doing averaging over multiple reading so this might be enough.

I plan to have the circuit inside the cabin as it's not water proof and has an overtemp buzzer.

Michael